A low-dimension quantum dot semiconductor nanomaterial has excellent photoelectronic properties because of its special electronic structure and density of states, which may widely be applied to various fields such as nanoelectronics, photoelectronics, life sciences and quantum computation. It is indicated with theoretical analysis that a quantum dot laser has better performance than a quantum well laser, for example, higher gain, lower threshold current, higher quantum efficiency, better thermal stability. In addition, the quantity of electrons entering into or leaving away from quantum dots may be precisely controlled in a single electron with an electron tunneling effect of the quantum dots. Therefore, a single-electron transistor may be manufactured. The quantum dots may be probably applied in solid-state quantum computation, a photon detector with vertical incident light, etc.
A Stranski-Krastanow (S-K) self-organized growth is a method for manufacturing a quantum dot material, which is mostly researched by scientists in the world and has an important application value. A basic principle of the S-K self-organized growth is described as follows. In an exptaxial growth process such as Molecular Beam Epitaxy (MBE) of a semiconductor material with a lattice constant different from a substrate, the lattice constant in the direction of the growth is different from that of a substrate, and a lattice stress is accordingly caused. When accumulating to a certain extent, to release the lattice stress, atoms at a surface may be migrated and clustered, and/or a misfit dislocation may be generated. In the case of atoms at a surface migrating and aggregating, atom clusters grow and are buried in an epitaxial material to be grown, so as to form the quantum dots. Initial atom clusters formed for releasing the lattice stress are seeds of the quantum dots and the quantum dots are formed from the seeds. The seeds are formed because of statistical thermodynamics fluctuation, the locations and sizes of the seeds and the speed of forming the seeds are totally random. This is the so called S-K dynamic random growth mechanism of the quantum dots.
As shown in FIG. 1A, the quantum dots currently applied in devices are all disorderly grown with the S-K self-organized epitaxial growth (dynamic random growth). The quantum dots obtained with this approach are defect-free and applicable to the manufacture of devices. It is also proved that the performance of the quantum dot material is obviously better than other materials for similar devices. However, some key parameters such as the sizes and distribution of the quantum dots are random and uncontrollable. Thus, repeatability of production is poor and industrialization is hard to be implemented. The quantum dots grown with this approach cannot be used to manufacture quantum information devices. Even though a few workable devices are found from the devices manufactured in scale, performances of the workable devices may significantly differ from each other. Because the disorderly quantum dots have a wide gain spectrum, it is hard to use the disordered quantum dots to manufacture a high power laser. Short-range ordered quantum dots shown in FIG. 1B are obtained by jetting an etching gas to a substrate to etch some micropores on the substrate and then growing the quantum dots at the micropores. Comparing with disordered self-organized quantum dots, the quantum dots obtained with this approach are ordered in some extent. However, the processing of micropores etching induces large amount of etching defects, which may be maintained and even magnified in the growth of the quantum dots. Long-range ordered quantum dots shown in FIG. 1C are obtained by etching a substrate with common nanomanufacturing technologies to obtain a nano pattern template in advance and then epitaxially growing the quantum dots on the template. Defects introduced by the common nanomanufacturing technologies are worse both in size and scale than the defects caused by the micropores etched by the etching gas. Neither the short-range ordered quantum dots nor the long-range quantum dots may be used to manufacture workable devices because of the defects.
Consequently, how to manufacture long-range ordered quantum dots without a defect or with low defect density in large scale currently becomes a frontier and hot research filed of the low-dimension quantum dot semiconductor nanomaterial.